River Goyt and Etherow Crayfish Survey
Item Type monograph
Publisher Environment Agency
Download date 24/09/2021 21:12:28
Link to Item http://hdl.handle.net/1834/27174 Scientific Investigations Database Project ENVIRONMENT AGENCY
RIVER GOYT & ETHEROW CRAYFISH SURVEY
August-November 2000 Acknowledgements
Many thanks all those who helped with the River Etherow-Goyt Crayfish Survey, including members of the Friends of Etherow Country Park, Stockport Metropolitan Borough Council and the Etherow-Goyt Partnership River Valley Initiative.
I would particularly like to thank Beth Irvine, co-ordinator of the Etherow-Goyt Partnership and John Rowlands, formerly the Countryside Ranger at Etherow Country Park for helping to make the project a success.
The Environment Agency and the Etherow-Goyt Partnership, (a local river valley initiative) funded this project.
This report was prepared by Keith Atkinson of the Ecology Section, Environment Agency, Appleton House, 430 Birchwood Boulevard, Birchwood WA3 7WD. CONTENTS
Section Page
1- Background 1
2- Approach 1
3- Results 2
4- Discussion 2
5- Summary 4
Appendices 7 1- BACKGROUND
The Environment Agency through its multi-functional project budget part-funded the River Goyt/Etherow Crayfish Survey, a joint venture with the Etherow-Goyt Partnership River Valley Initiative. The project began with a training day on the 29th of July and followed by a survey programme between August and October 2000.
The project was based on the need to verify the presence of the non-native American signal crayfish (Pacifastacus leniusculus) in the main River Goyt, and determine its distribution. Signal crayfish have been reported in the River Goyt after spreading from a known population centre in Hollywood End Brook, to the east of Marple Bridge.
The information collected as part of this project is important in assessing the threat to an important population of native white-clawed crayfish (Austropotamobius pallipes), a protected species1. The only known population of native crayfish in the Mersey system is in a tributary of the River Goyt, approximately 15.5 kilometres upstream of Marple Bridge. More information on the distribution of crayfish species in the Mersey/Weaver system is contained in Figure 2.
2- APPROACH
The project was run using volunteers from the Friends of Etherow Country Park and the Etherow-Goyt Partnership. All volunteers were provided with basic training relating to crayfish and their ecology, survey techniques and relevant legislation.
Crayfish trapping kits were provided to groups of registered volunteers who then selected a stretch of the river on which to set their traps. In addition, several volunteers undertook manual searches. Traps were baited with a variety of fish products and left in areas of watercourse containing favourable crayfish habitat.
The teams were asked to record their findings on a standard recording sheet, which was supplied with the trapping kits.
* Priority species in UK Biodiversity Action Plan Steering Group Report, protected under Schedule 5 of the Wildlife & Countryside Act, 1981 & included in Annexes II and IV of the European Habitats Directive 2
3- RESULTS
The majority of groups based their surveys on trapping only. Fifteen different locations were surveyed from Black Brook (near Chapel-en-le-Frith) to Chadkirk on the main River Goyt (see Figure 1).
Three positive results were recorded, all of which were downstream of Marple Bridge (see Figure 1 and Appendix 1). Signal crayfish were found at least 8 kilometres downstream of their suspected source on Hollywood End Brook. No crayfish were found upstream of Marple, although trapping intensity/duration was less in this stretch.
All the specimens recorded were associated with boulder/cobble substrate, and were found in the margins of the watercourse. The majority of specimens recovered were male (60%- see with Appendix 1). The largest specimen was an adult male had a carapace length of 150mm.
4- DISCUSSION
The results show that American signal crayfish have spread at least 8 kilometres downstream of Hollywood End Brook. It is probable that their range is greater than this as water quality is no longer a barrier to their spread. Recent biological surveys undertaken by the Environment Agency have found pollution tolerant insect larvae as far downstream as Stockport town centre.
Although no signal crayfish were found in the River Goyt above of Marple Bridge, they are likely to have spread upstream. The nearest known obstacle to crayfish migration is a weir approximately 1.8 kilometres upstream of the confluence of Hollywood End Brook with the River Goyt.
The range of the signal crayfish population downstream of Marple Bridge indicates relatively rapid colonisation of the lower river, given the width, depth and relatively diverse habitat in this reach. An accurate estimate of their rate of spread cannot, however, be calculated in the absence of data regarding the original escape of the crayfish into Hollywood End Brook. A 3
rough estimate of the rate of spread downstream is between 0.4 and 0.6 kilometres per year, based on the signal crayfish introduction taking place 15-20 years ago.
A key finding of the survey was that the design of the traps might have allowed crayfish to evade capture under certain conditions. As results after the first month of survey work were all negative (no crayfish captured), it was decided that a trial of the traps should take place in a known signal crayfish location (Hollywood End Brook). Overnight trapping with one trap yielded four signal crayfish, indicating that the design of the traps may not be a problem if:
• The survey location has a high population density of crayfish; • The openings of trap are secure and constructed to the recommended aperture size; and • The traps are regularly inspected
Observations from one surveyor, however, indicated that the ‘funnel-shaped’ openings of the traps might have helped larger crayfish to evade capture by allowing them to climb back out of the trap once they had taken the bait.
In addition to the long-term threat to native crayfish, there are potential problems for anglers, mainly through bait stealing. There have been three reports to the Environment Agency Ecology section of crayfish taking anglers bait, two of which were by anglers fishing in the River Goyt between Chadkirk and Marple Bridge. In one location on the River Goyt (Wyevale Garden Centre, Chadkirk) there have been reports of crayfish taking food thrown in by workers.
Results from the Goyt-Etherow Crayfish Project confirm the presence of signal crayfish in the main River Goyt. It is certain that this population will continue to expand its range in the River Goyt, and in the Mersey-Weaver system as a whole.
Results from this survey show a need to monitor the upstream spread of signal to help plan the protection of native crayfish populations upstream. 4
5- SUMMARY
• North American Signal Crayfish (Pacifastacus leniusculus) are present in the main
River Goyt, having spread from Hollywood End Brook;
• Signal crayfish have spread at least 8 kilometres downstream;
• The current downstream rate of spread is estimated at between 0.4 and 0.6
kilometres per year;
• Trap design/trapping for any future work may need to be modified; and
• Future work should focus on stretches of the River Goyt immediately upstream of
the signal crayfish source. Figure 1-Results of Crayfish Survey of the River Goyt: August-October 2000
7
APPENDIX 1- Signal crayfish records for the River Goyt, August-October 2000
Location Grid Ref. Carapace Sex Habitat length (mm) (male/female) River Goyt opposite Wyevale SJ938896 150 male boulder/ Garden Centre (rear of factory) cobble 105 male boulder/ cobble 100 female boulder/ cobble Small tributary, off River SJ936895- 375* male boulder/ Goyt, near Hare & Hounds SJ936893 cobble public house 100* female boulder/ cobble 125* female boulder/ cobble Hollywood End Brook, u/s SJ864898 102 male boulder/ Mellor Bridge, Marple Bridge cobble village 100 female boulder/ cobble 86 male boulder/ cobble 55 male boulder/ cobble
x - Measurement o f length may have included claws
APPENDIX 2: Equipment used for the survey
• Two crayfish trap kits each containing 10 self assembly crayfish traps with bait bag, anchor line and cable ties as supplied by GB Nets Ltd (formerly of Burnley Road, Todmorden, Lancashire but currently under new ownership)
• Professional hand-net as supplied by GB Nets.
APPENDIX 3: Participants in the Goyt-Etherow Crayfish Survey
John Rowland (Ranger Etherow Country Park), Jim Smith, Alan Cassidy, Heather Stewart, Barbera Bird, Diana Findley, Bernard & Rhian Law, Chris Barlow, Melanie Cove, Bob Perkins, Mary Lee, Michelle Pryke, Andrew Bennison and Charles Hamilton.